{"id":"CVE-2021-42387","url":"https://www.cyber-defence.io/tools/cve/CVE-2021-42387","generatedAt":"2026-10-27T20:53:37.995Z","title":"Heap out-of-bounds read in Clickhouse's LZ4 compression codec when parsing a malicious query.","description":"Heap out-of-bounds read in Clickhouse's LZ4 compression codec when parsing a malicious query. As part of the LZ4::decompressImpl() loop, a 16-bit unsigned user-supplied value ('offset') is read from the compressed data. The offset is later used in the length of a copy operation, without checking the upper bounds of the source of the copy operation.","published":"2022-03-14T23:15:08.000Z","lastModified":"2026-06-17T04:09:45.000Z","status":"Modified","sourceIdentifier":"reefs@jfrog.com","cvss":{"version":"3.1","score":8.1,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H"},"cwe":["CWE-125"],"affected":["clickhouse/clickhouse","debian/debian linux"],"epss":{"score":0.01573,"percentile":0.75242,"date":"2026-10-26","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (1.57%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[],"references":[{"url":"https://jfrog.com/blog/7-rce-and-dos-vulnerabilities-found-in-clickhouse-dbms","tags":["Exploit","Third Party Advisory"],"source":"reefs@jfrog.com"},{"url":"https://lists.debian.org/debian-lts-announce/2022/11/msg00002.html","tags":["Mailing List","Third Party Advisory"],"source":"reefs@jfrog.com"},{"url":"https://jfrog.com/blog/7-rce-and-dos-vulnerabilities-found-in-clickhouse-dbms","tags":["Exploit","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.debian.org/debian-lts-announce/2022/11/msg00002.html","tags":["Mailing List","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2021-42387","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}